Crane Song AVOCET II - Manual (Page 40)

range speaker instead of spikes. Whichever mounting method, the goal is to reduce sympathetic
vibrations or traveling waves in cabinets, floor and walls. The resonant frequency of the box and stand
should be extremely low. Hit the box with your fist and confirm it does not have a resonant character;
sweep a sine wave through the system and listen for vibrations. I’ve had great success with a very
thin isolator between the speaker and the stand which compresses almost completely under the
speaker’s weight.
Listener position
If you’re sitting in an antinode, there’s always going to be a dip at that frequency, and no amount of
equalization will correct the acoustic problem.
Speaker position
Ironically, solid walls aggravate the interaction of loudspeaker position and frequency response. The
closer the loudspeaker to walls and especially corners, the greater the bass level. You may have the
“smoothest,” most accurate satellite (main) speakers in the world, but they must be positioned to avoid
side wall reflections and must be far enough from all walls to reduce resonances.
Near Field Monitoring?
I wouldn’t master with near-field monitors, but I will mix with them. Near-field monitoring was devised
to reduce the effects of adverse room acoustics, but if your room acoustics are good, then “Mid-field”
or “Far-field” will provide a more accurate depth and spatial picture. There must be an obstruction-free
path between the monitors and the listener. What is the biggest impediment to good sound
reproductionin a recording studio? The console. No matter how you position the monitors, the
console’s surface reflects sound back to your ears, which causes
comb filtering , the same tunnel
effect you get if you put your hand in front of your face and talk into it. Or if you wear a wide-brimmed
hat, which produces an irregular dip around 2 kHz. It amazes me that some engineers aren’t aware of
the deterioration caused by a simple hat brim! Similarly, I shudder when I see a professional
loudspeaker sitting on a shelf inches back from the edge, which compromises the reproduction. The
acoustic compromise of the console can only be minimized, not eliminated, by positioning the
loudspeakers and console to increase the ratio of the direct to reflected path. Lou Burroughs’ 3 to 1
rule can be applied to acoustic reflections as well as microphones, meaning that the reflected path to
the ear should ideally be at least 3 times the distance of the direct path.
What about measurements?
Can’t we just measure, adjust the crossovers and speaker position for flattest response, then sit down
and enjoy? Well, since no room or loudspeaker is perfect, measurements are open to interpretation,
and frequency response measurements will always be full of peaks and dips, some of which are more
important to the ear than others. Which of those many peaks and dips in the display are important
and which ones should we ignore?
I’ve found the ear to be the best judge of what’s important, especially in the bass region. The ear will
detect there’s a bass problem faster than any measurement instrument. The measurement instrument
will help to pinpoint the specific problem frequencies, whether they’re peaks or dips, and by supplying
numbers, aid in making changes. The whole process is very frustrating, and it’s inspired my search for
setup and test methods that use the ear. A perfect setup still requires a multistep process: listen,
measure, adjust, listen again, and repeat until satisfied, but it’s possible to streamline that process.
Here’s a listening test for adjusting subwoofer crossovers that uses simple, readily obtainable and
cheap test materials, and that’s generally as precise as most more formal measurement techniques!
If you’re setting up a permanent system, dedicate a day to the process; even the easy doesn’t come
easy. Some brands of subwoofer amplifiers have all the controls or connectors you need; you may
have to adapt the process described below to your particular woofer system.
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